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The Load Planning Problem at an Intermodal Railroad Terminal A. K. Nemani, K. C. Jha, and R. K. Ahuja, Submitted to Transportation Research B. 2009 In this paper, we study the load planning problem (LPP) arising at an intermodal railroad terminal. The LPP is to assign the containers and trailers on the given set of railcars for maximizing train utilization and aerodynamic efficiency. The solution to the problem must also satisfy several operational and regulatory requirements. We formulate the LPP as an integer program on an underlying network and solve it to optimality using CPLEX. The run-time of the CPLEX optimizer increases exponentially with the network size and other specifications, and it fails to solve modest-sized problems in a reasonable amount of time. To efficiently solve these real-life instances, we propose two multi-exchange neighborhood search algorithms. Finally, we combine MIP and multi-exchange neighborhood search algorithms to develop a hybrid algorithm. Our empirical studies demonstrate that these algorithms, especially the hybrid algorithm, are able to solve modest-sized problems in a very reasonable time and can be used in practical applications. An additional advantage of our approach is its flexibility in incorporating new business requirements. |